Method of examining locations in a wafer with adjustable navigation accuracy and system thereof

ABSTRACT

Data indicative of alignment targets may be received. Each alignment target may be associated with a target location on an object. Locations of the object to be inspected may be identified. An alignment target from the alignment targets may be selected. Each of the locations may be within a determined distance from the selected alignment target. An indication may be provided to align the object relative to an examination tool for inspecting the locations within the determined distance from the selected alignment target.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/222,824 filed on Jul. 28, 2016, the contents of which are herebyincorporated by reference

TECHNICAL FIELD

The presently disclosed subject matter relates to location-basedexamination of objects such as semiconductor wafers, masks and the like,and more particularly to increasing the efficiency and accuracy of suchexamination.

BACKGROUND

Various objects such as semiconductor wafers, masks, printed circuitboards, solar panels and microelectromechanical devices are manufacturedby manufacturing processes that are highly complex and costly, comprisemultiple stages, and require very accurate machines.

Current demands for high density and performance associated with ultralarge scale integration require formation of device features with highprecision and uniformity. The usage of such device features necessitatesautomated process monitoring, including frequent and detailedexamination of specimens during the manufacturing process.

The term “examination”, unless specifically stated otherwise, used inthis specification in relation to a wafer, should be expansivelyconstrued to cover any kind of examination, including but not limited todetection and/or classification of defects in an object (for example,semiconductor wafers) provided by using non-destructive inspectiontools. By way of non-limiting example, examination can includegenerating one or more recipes for examination and/or parts thereof,runtime inspection (e.g. scanning in a single or in multiple scans),reviewing, and measuring and/or other operations provided with regard tothe wafer or parts thereof using the same or different inspection tools.Such examination can be carried out by optical examination techniques,charged-particle examination techniques (such as electron beam and ionbeam techniques), metrology tools, or any other known technique or tool.

In the context of examination by way of defect detection, in order tofind defects, various examination steps can be integrated into themanufacturing process, including inspection and review. The examinationsteps can be performed a multiplicity of times, for example at certainstages such as after the manufacturing or processing of certain layers,or the like.

The term “defect” used in this specification should be expansivelyconstrued to cover any kind of abnormality in examination results orundesirable feature formed on or within a wafer. The term “defect” mayrelate to a location on a wafer that is identified as a location of asuspected defect, a location of interest representing a location to befurther reviewed, and a location that is identified as a location of aredetected defect or a classified defect. A variety of non-destructiveinspection tools includes, by way of non-limiting example, scanningelectron microscopes, atomic force microscopes, optical inspectiontools, metrology, etc. While in some contexts the defect location mayrefer to a single point, whether in two or three dimensional space, inother contexts the term may relate to a space containing a possibledefect, such as a one, two or three dimensional area.

By way of non-limiting example, examination can employ a two phase“inspection and review” procedure.

The term “inspection” refers to scanning and analyzing a wafer or a partthereof, in order to detect locations in which defects may be found.Suspicious locations reported by inspection may include true defects,false positive reports, and nuisance defects, which are harmless.

The term “review” refers to capturing and analyzing one or more specificlocations, for example locations of possible defects reported by theinspection process, locations of interest derived from design data, etc.In some embodiments, the term “review” may also refer to, mutatismutandis, to performing metrology procedures.

Typically, inspection is performed at higher speed and lower resolutionthan review. Thus, inspection can be used for covering larger areas anddetecting possible defects, wherein some or all of which may later bereviewed and examined.

In some embodiments, inspection and review can be performed by differenttools, but in other embodiments they can be performed by the same tool.

The complex manufacturing process is not error-free and such errors maycause faults in manufactured objects. Such faults may include defectsthat can harm operation of the object, false positive findings, whichmay seem to contain a defect, but no actual defect exists at the area,and nuisances, which may be defects but do not cause any harm ormalfunction of the manufactured unit. Errors may include linear ornon-linear errors, such as mechanical, electrical or optical errors, inaddition to faults in the raw material, human errors and others maycause defects in the wafers. Additional errors may be caused byspatio-temporal factors, such as temperature changes of the wafer,occurring after one or more captures, which may cause slightdeformations of the wafer.

GENERAL DESCRIPTION

In accordance with certain aspects of the presently disclosed subjectmatter, there is provided a method of examining an object using aprocessor operatively connected to a memory, the method comprising:accommodating, in the memory, data indicative of a plurality ofalignment targets, each alignment target associated with a targetlocation on an object; accommodating, in the memory, a plurality oflocations to be captured; and selecting, by the processor, an alignmenttarget subset of the plurality of alignment targets, such that each ofthe plurality of locations is associated with and is within a determineddistance from a single alignment target from the alignment targetsubset, the distance determined in accordance with a provided field ofview, and wherein the alignment target subset comprises fewer targetsthan locations to be reviewed, the alignment target being usable foraligning the object relatively to an examination tool for capturing thelocations associated with the single alignment target. The method canfurther comprise: for at least a first location of the plurality oflocations: aligning the object such that a capture device can capture analignment target associated with the first location; capturing by theexamination tool a first image of the object including the alignmenttarget; determining an actual location of the alignment target in thefirst image; determining a transformation between the actual locationand the target location of the alignment target; moving the object suchthat an examination tool captures a transformed location obtained byapplying the transformation to the first location; and capturing asecond image of the object including the transformed location. Themethod can further comprise: once an object is received for examination:receiving a list comprising one or more proximate locations for pointsof interest on the object; determining a target having a locationclosest to one of the proximate locations; aligning the objectrelatively to the examination tool in accordance with the location; andcapturing a part of the object including the point of interest. Themethod can further comprise: for at least a first location, and a secondlocation associated with a different alignment target than the firstlocation: determining a first reference location, a second referencelocation, corresponding, respectively, to the first location and thesecond location, and a second alignment target common to the firstreference location and the second reference location, all located in onearea which is different than areas of the first location and the secondlocation. The method can further comprise: moving the object such thatthe examination tool captures the second target; capturing a third imageof the object including the second target; determining an actual secondreference target location within the third image; determining areference transformation between the actual reference target locationand the a location of the second target; moving the object such that theexamination tool captures a first transformed reference locationobtained by applying the reference transformation to the first referencelocation; and capturing a fourth image of a fourth part of the objectincluding the first transformed reference location; moving the objectsuch that the examination tool captures a second transformed referencelocation obtained by applying the reference transformation to the secondreference location; and capturing a fifth image of a fifth part of theobject including the second transformed reference location; and subjectto detecting differences between areas of the second image associatedwith the first transformed location and of the fourth image associatedwith the first transformed reference location, indicating a defect inthe object. The method can further comprise: for at least the firstlocation, and a second location associated with the alignment target ofthe first location: determining a first reference location and a secondreference location, corresponding, respectively, to the first locationand the second location associated with a common alignment target,wherein the first reference location, the second reference location andthe alignment target are located in one area which is different but at amaximal predetermined distance from areas of the first location and thesecond location. The method can further comprise: moving the object suchthat the examination tool captures a first transformed referencelocation obtained by applying the transformation to the first referencelocation; and capturing a third image of a third part of the objectincluding the first transformed reference location; moving the objectsuch that the examination tool captures a second transformed referencelocation obtained by applying the reference transformation to the secondreference location; and capturing a fourth image of a fourth part of theobject including the second transformed reference location; and subjectto detecting differences between areas of the first image and the thirdimage associated with the first location, indicating a defect in theobject. Within the method, transformation is optionally a twodimensional transformation. The method can further comprise: receivingone or more review locations or one or more regions of interest from ahuman user. Within the method, the target subset is optionally selectedusing clustering. Within the method, the target location and firstlocation are optionally indicated in coordinates associated with designdata of the object. The method can further comprise: receiving designdata of the object; rasterizing a synthetic image of the object, basedon the design data; and determining the plurality of targets locationsby applying image processing techniques to the synthetic image. Themethod can further comprise: receiving some of the design data for oneor more potential target locations; and determining exact targetlocation by applying processing techniques to the design data. Withinthe method the plurality of targets are determined in accordance withuniqueness in an area surrounding each target, or such that an areasurrounding each target comprises a multiplicity of edges in at leasttwo directions. The method can further comprise validating the targetlocations against an image of the object. Within the method, theplurality of targets optionally include a primary target and a secondarytarget for each region of the object. Within the method, each of theplurality of locations is optionally associated with a single alignmenttarget. Within the method, the examination tool is optionally an opticalinspection device or a charged particle beam based examination tool.

In accordance with other aspects of the presently disclosed subjectmatter, there is provided a computerized system for examining an object,the system comprising a processor configured to: accommodate in thememory data indicative of a plurality of targets, each target associatedwith a target location; accommodate in the memory a plurality of reviewlocations to be captured; and select by the processor an alignmenttarget subset of the plurality of targets, such that each of theplurality of locations is associated with and is within a determineddistance from a single alignment target from the target subset, thedistance determined in accordance with a provided field of view, andwherein the alignment target subset comprises fewer targets thanlocations in the review locations, the alignment target being usable foraligning the object relative to an examination tool for capturing thelocations associated with the single alignment target.

In accordance with other aspects of the presently disclosed subjectmatter, there is provided a computer program product comprising acomputer readable storage medium retaining program instructions, whichprogram instructions, when read by a processor, cause the processor toperform a method comprising: accommodate in the memory data indicativeof a plurality of targets, each target associated with a target locationon an object; accommodate in the memory a plurality of locations to becaptured; and select by the processor an alignment target subset of theplurality of targets, such that each of the plurality of reviewlocations is associated with and is within a determined distance from asingle alignment target from the target subset, the distance determinedin accordance with a required accuracy, and wherein the alignment targetsubset comprises fewer targets than locations to be reviewed, thealignment target being usable for aligning the object relative to anexamination tool for capturing the locations associated with the singlealignment target.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the present disclosure and to see how it can becarried out in practice, embodiments will be described, by way ofnon-limiting examples, with reference to the accompanying drawings, inwhich:

FIG. 1A is a generalized block diagram of a computerized environment forexamining a wafer in accordance with some exemplary embodiments of thedisclosure;

FIG. 1B illustrates a generalized flowchart of an examination process ofa wafer, in accordance with some exemplary embodiments of thedisclosure;

FIG. 2 illustrates a generalized flowchart of examining a wafer inaccordance with some exemplary embodiments of the disclosure;

FIG. 3A shows an exemplary illustration of targets and review locationson a wafer die, in accordance with some exemplary embodiments of thedisclosure;

FIG. 3B shows an exemplary graph for a particular examination device,upon which the accuracy parameter is determined;

FIGS. 4A, 4B and 4C show schematic illustrations of exemplary clusteringoptions for review locations and targets on a wafer die, in accordancewith some exemplary embodiments of the disclosure;

FIGS. 5A, 5B, 5C and 5D show exemplary schematic illustrations ofmethods for using alignment targets when performing detection by meansof die to die comparison, in accordance with some exemplary embodimentsof the disclosure;

FIG. 6 shows a generalized flowchart of using alignment targets whenperforming detection by means of die to die comparison corresponding toFIG. 5C, in accordance with some embodiments of the disclosure;

FIG. 7 shows a generalized flowchart of using alignment targets whenperforming detection by means of die to die comparison corresponding toFIG. 5D, in accordance with some exemplary embodiments of thedisclosure; and

FIG. 8 shows a schematic block diagram of a system for reviewing reviewlocations, in accordance with some exemplary embodiments of thedisclosure.

DETAILED DESCRIPTION

For simplicity, aspects of the disclosure will be described withreference to examination of semiconductor wafers. The disclosure is notlimited to examination of wafers and is applicable to location-basedexamination of other objects such as lithographic masks and reticles,printed circuit boards, solar panels, microelectromechanical devices andother objects.

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the disclosure.However, it will be understood by those skilled in the art that thepresently disclosed subject matter can be practiced without thesespecific details. In other instances, well-known methods, procedures,components and circuits have not been described in detail so as not toobscure the presently disclosed subject matter.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing”, “computing”,“representing”, “comparing”, “generating”, “assessing”, “matching”,“updating” or the like, refer to the action(s) and/or process(es) of acomputer that manipulate and/or transform data into other data, saiddata represented as physical, such as electronic, quantities and/or saiddata representing the physical objects. The term “computer” should beexpansively construed to cover any kind of hardware-based electronicdevice with data processing capabilities.

The operations in accordance with the teachings herein can be performedby a computer specially constructed for the desired purposes or by ageneral-purpose computer specially configured for the desired purpose bya computer program stored in a non-transitory computer-readable storagemedium.

The terms “non-transitory memory” and “non-transitory storage medium”are used herein should be expansively construed to cover any include anyvolatile or non-volatile computer memory suitable to the presentlydisclosed subject matter.

The term “design data” used in the specification should be expansivelyconstrued to cover any data indicative of hierarchical physical design(layout) of a specimen. Design data can be provided by a respectivedesigner and/or can be derived from the physical design (e.g. throughcomplex simulation, simple geometric and Boolean operations, etc.).Design data can be provided in different formats as, by way ofnon-limiting examples, GDSII format, OASIS format, etc. Design data canbe presented in vector format, grayscale intensity image format orotherwise. Design data may comprise design structural elements thatrepresent different features to be formed on one or more layers of aspecimen. As known in the contemporary art, a design structural elementcan be constructed as a geometrical shape with a closed contour or ageometrical shape combined with insertion of other structural elements.By way of non-limiting examples, a given design structural element cancomprise one or more STRUCTURE elements inserted by means of SREF, AREFdirectives in GDSII format, or can comprise one or more CELL elementsinserted by means of PLACEMENT and REPETITION (OASIS format).

The term “review location” or “location” used herein should beexpansively construed to cover any location on a wafer required to bereviewed. A location may relate to a point, expressed as a set ofcoordinates in two or three dimensions, or to a line or two- orthree-dimensional area, depending on the context. Review locations maybe associated with revealed or potential defects, patterns of interest(e.g., crossing of specific design elements), or otherwise definedregions of interest determined during one or more examination stages.For example locations may be detected during inspection, by taking oneor more optical images of the wafer or part thereof, and comparing anobtained image or features therein to an expected image, topredetermined features from design data, or to an image of another die,which may be more or less adjacent, wherein the differences may beregarded as potential defects. The review locations may further includeany other locations it may be required to review, which may be providedautomatically, manually, or the like, provided by a user, or the like.Review location can be specified in design coordinates and/orcoordinates tied to a wafer, die, or a region thereof. It is noted thatthe review locations can be a subset selected for review among a largergroup of review locations of interest.

The term “alignment target” or “target” used herein should beexpansively construed to cover any wafer area recognizable within itsenvironment. For example, a recognizable image of a target can becharacterized by distinct features such as a pattern unique in itsenvironment, a multiplicity of edges in two or more dimensions, or thelike. Each target is associated with a target location, expressed forexample as two coordinates in a predetermined coordinate system (e.g.design coordinates and/or coordinates tied to a wafer, die, or partsthereof). Targets can be useful in navigating to and capturing one ormore review locations.

The term “reference location” should be expansively construed to cover alocation corresponding to another location specified in a set ofcoordinates tied to a certain point or area of the wafer. For example,when a wafer comprises a multiplicity of allegedly identical dies, alocation having a set of coordinates relative to one die may beassociated with one or more reference locations located at the same setof coordinates relative to another die.

Reference is now made to FIG. 1A, showing a computerized environment forexamining a wafer, according to some embodiments of the disclosure.

FIG. 1A illustrates examination component 100, inspection tool 104,review tool 108, alignment target selection component 112, and designdata storage 122.

A network 128 is coupled to examination component 100, inspection tool104, review tool 108, alignment target selection component 112, anddesign data storage 122. For example, network 128 may be a fabcommunication system. For simplicity of explanation, only a singleinspection tool 104 and a single review tool 108 are shown. It should benoted that in practice, a plurality of inspection tools and a pluralityof review tools can be connected via network 128. For further simplicityof explanation, a single alignment target selection component 112 and asingle examination component 100 are shown. It should be noted, however,that more than one alignment target selection component 112 or more thanone single examination component 100 can be used. Additionally oralternatively, each of alignment target selection component 112 andexamination component 100 can be implemented as one or moreinterconnected computing platforms.

The disclosure is not limited by the type of physical communication andcoupling provided between the various entities of FIG. 1A. Any twocomponents may be connected directly, via network 128, via any othercomponent, whether such component is shown or not in FIG. 1A.

Although for simplifying the explanation alignment target selectioncomponent 112 and examination component 100 are shown as stand-alonecomputer systems, it is noted that any of them can be a part ofinspection tool 104 or of review tool 108. Alternatively, alignmenttarget selection component 112 and examination component 100 can beimplemented as one computer system. According to some embodiments of thedisclosure, one or more of alignment target selection component 112 andexamination component 100 can be facilitated as a hardware utility whichis placed on an electronic rack of, for example, inspection tool 104,review tool 108 or any other computing system associated with the fab.

Examination component 100 can be configured to execute the methods ofFIG. 1B (including activating alignment target selection component 112),6 and 7 below, and alignment target selection component 112 can beconfigured to execute step 150 of FIG. 1B below.

Alignment target selection component 112 can include a memory unit 116and a processor 118.

Memory unit 116 can be configured to store at least one of: informationrequired for executing a method such as depicted in step 150 anddetailed in FIG. 2, and software required for executing any of saidmethod, or information generated during the execution of said method.

Processor 118 can be configured to perform any operation required duringany step of one or more of the method such as depicted in step 150 anddetailed in FIG. 2.

Examination component 100 can include a memory unit 120 and a processor124.

Memory unit 120 can be configured to store at least one of: informationrequired for executing one or more of the methods depicted in FIGS. 1B,6 and 7, and software required for executing any of said methods, orinformation generated during the execution of said methods.

Processor 124 can be configured to perform any operation required duringany step of one or more of the methods depicted in FIGS. 1B, 6 and 7.Referring now to FIG. 1B, this shows a generalized flowchart ofexamining a wafer, in accordance with some exemplary embodiments of thedisclosure. The flowchart is described in association with the elementsof FIG. 1A described above.

It will be appreciated that the examination process can repeat multipletimes, for different layers, or different parts of the wafer, differentstages on the manufacturing process, or the like.

Examination component 100 detailed below can be configured to obtainreview locations (140).

As illustrated in FIG. 1B, examination component 100 can be configuredto obtain a multiplicity of targets (144) provided by a user, determinedautomatically, or the like. Each target may be associated with a targetlocation indicating its coordinates, for example its top left corner, ifapplicable. Each target may be square, rectangular, cyclic, or may haveany other shape. The targets may be obtained, for example, bycalculations that use design data stored in design data storage 122which may also be implemented as a memory device collocated with memory116, memory 120 or separately.

Examination component 100 can be configured to activate alignment targetselection component 112 for selecting (150), out of the receivedtargets, targets usable for navigating to review locations and uniquewithin their surrounding area, such targets being referred tohereinafter as “alignment targets”. The alignment targets can beaccommodated in memory.

As will be further detailed with reference to FIGS. 3, 4A-4C and 5A-5Dbelow, the alignment targets are used during navigation. The review toolcan apply a navigation process for navigating to a possible defect inorder to capture the possible defect and its environment, and thennavigate to further ones and capture them as well.

Navigation to a location may be widely construed to cover moving thewafer within or relative to the review tool, such that the review toolmay perform an action, such as capture an image of the review location.Alternatively, and depending on the review tool, one or more members ofthe review tool may be moved relative to the wafer.

However, the navigation process may suffer from navigation errors thatmay cause the review tool to capture a wrong location when reviewing asuspected defect. Such navigation errors may stem from a number ofcauses. Errors may relate to inaccuracies in the locations as receivedfrom the inspection tool, to mechanical inaccuracies preventing accuratenavigation, to inaccuracies in translations between the variouscoordinate systems used, including for example the design datacoordinate system, the inspection coordinate system and the reviewcoordinate system, or others. Errors may also be caused byspatio-temporal factors, such as temperature changes of the waferoccurring after one or more possible defects have been captured, whichmay cause slight deformations of the wafer. Further errors may besubject to ambiguity in identifying the wafer elements captured at thelocation. It will be appreciated that further errors may occur due toother reasons.

Some exemplary embodiments of the disclosure provide a method forreducing navigation errors of an examination tool in examining anobject, to thereby ensure that the navigation error when examining anobject at one or more locations at a given field of view shall notexceed the given field of view.

In accordance with certain embodiments of the presently disclosedsubject matter, in order to overcome the navigation errors and capturethe required review locations, alignment targets can be used. Thealignment targets can be specified in a coordinate system which may beknown at all examination stages, for example the coordinate systemavailable during the design of the wafer, e.g., the Computer AidedDesign (CAD) data coordinate system, which is also available during theinspection and review stages.

The navigation process is characterized by a required accuracy value,typically provided by a user, or determined upon a field of view givenfor a certain examination device. The accuracy value indicates themaximal radius for which the navigation error is smaller than the fieldof view and is therefore acceptable. Thus, the accuracy may be describedas the maximal distance between a designated location to which it isrequired to navigate the wafer relatively to the review tool, and thelocation to which the wafer has been navigated. For example, if thedesignated coordinates of an object are [100, 100], then if the accuracyis 1 micron, then the object is guaranteed to be within a circle boundby x=99, x=101, y=99 and y=101 (all in microns). Thus, a field of viewbound by a square of at least 2 micron*2 micron centered aroundcoordinates [100,100] ensures that the object is present within thecaptured image. The alignment target shall be selected to enable itunambiguous identification within the field of view.

As technology progresses, the pixels grabbed by the imaging devices needto and indeed get smaller, therefore more pixels are required forcovering the same area, thus increasing the image acquisition time, andalso limiting the number or locations it is practical to review. Thetime increase and number of locations limitation is particularly truewhen capturing with a scanning electron microscope.

If the navigation errors are high, then in order for each of the reviewlocations to be within the required accuracy from one of the targets, itmay be required to select more targets wherein each target is used fornavigating to fewer review locations, which will increase the overallreview time.

Thus, the accuracy may be selected as the maximal distance between atarget and a review location for which the navigation error is below thefield of view.

Reference is now made to FIG. 3B, showing an exemplary graph of therelationship between the navigation error when navigating from a targetto a location and the distance between the location and the target, fora particular device. In view of the graph, the maximal distance from analignment target may be selected to ensure navigation error is stillsmaller than the desired field of view radius. The desired field of viewis derived from the grab time and pixel size and defines the number oflocations which can be reviewed in a given period of time, for examplewithin an hour. For example, if the desired field of view has a radiusof 0.07 um, then an alignment target should be found in a radius smallerthan 3.6 um from the review location. Navigating from alignment targetwith a distance smaller than 3.6 um from the review location guaranteesthat the review location will be found within the 0.07 um radius.

It will be appreciated that large navigation errors imply a requirementfor grabbing an area of larger radius around the target. For a givennumber of pixels per captured image, the implication is lowerresolution. Increasing the resolution, however, will consume more timeand may thus limit the number of reviewed locations.

Navigation errors are becoming a more challenging aspect as the designrule of the printed circuit patterns, for example 20 nanometer, 10nanometer, and so on, keeps getting smaller.

Therefore, in accordance with certain embodiments of the currentlypresented subject matter, in order to review more locations at higheraccuracy, an approach of local alignment can be used.

It will be appreciated that a tradeoff exists between the speed andaccuracy of the review process. Using more alignment targets providesfor higher accuracy and higher time requirements due to a larger numberof full navigation processes being required, while using fewer alignmenttargets provides for lower accuracy and lower time requirements.

Typically, a few alignment targets are indicated for a wafer, such asbetween 5 and 20. However, a large distance between a target and alocation to be reviewed may introduce further deviations and errors.Thus, multiple targets can be defined for each wafer, for example over agrid. Each location can then be navigated to by using a nearby target.However, the navigation to the target associated with each location islengthy, since full alignment is required for each review location. Inorder to reduce the review time, a subset of the targets, to be used asalignment targets can be selected, such that each alignment target isused for navigating to a multiplicity of review locations, thussignificantly reducing the navigation time and enabling the review ofmore review locations.

Thus, at step 150, a subset of the targets can be selected as alignmenttargets in accordance with the review locations to be reviewed and theaccuracy, to provide for navigation and capturing of the reviewlocations with enhanced accuracy and efficiency.

The subset of the alignment targets can be selected such that eachreview location is associated with and at a distance not exceeding athreshold from one of the alignment targets. Selecting an alignmenttarget per each review location can enable accurate navigation, but mayintroduce the same spatio-temporal errors, causing a long reviewprocess, since a separate alignment is required per each reviewlocation. Thus it can be attempted to reduce the number of the alignmenttargets such that for at least one alignment target, a multiplicity ofreview locations are associated with the alignment target, and at adistance of at most the predetermined threshold therefrom. Thus, withone alignment operation it can be possible to navigate to the area of amultiplicity of review locations, such that after an initial navigationto the alignment target, only a short additional move is required fornavigating to each of the review locations associated with the alignmenttarget.

Examination component 100 can be configured to associate (152) eachreview location with an alignment target, for example the alignmenttarget that is closest to the location, the alignment target associatedwith a cluster to which the review location is assigned as detailedbelow, etc.

Examination component 100 can be configured to activate review (154) ofthe review locations. As further detailed below, reviewing can beperformed by navigating to one or more of the review locations. Inaccordance with certain embodiments of the presently disclosed subjectmatter, in order to navigate to a review location, the review tool canfirst navigate to an alignment target close to the required reviewlocation, capture a wafer area comprising the alignment target andidentify the alignment target within the captured image. The review toolcan then determine the transformation between the expected location andthe actual location, apply the transformation to the associated reviewlocation, and navigate to the review location in accordance with thecoordinates corrected by the applied transformation. The enabledrelative proximity between the review location and the alignment targetensures that the transformation obtained for the alignment target isalso applicable to the review location, such that the review locationwill indeed be captured in accordance with the required accuracy

Referring now to FIG. 2, showing a generalized flowchart of steps in amethod for reviewing a wafer, in accordance with some exemplaryembodiments of the disclosure.

Alignment target selection component 112 can be configured to performalignment target selection (150) from the available targets once thereview locations to be reviewed are available. Examination component 100can activate review location review (154) performed for reviewing thewafer at the review locations.

Alignment target selection step 150 can include step 208 for obtainingand accommodating in memory a plurality of targets. The targets can bereceived from a storage device, from a user, from a third party or anyother external source. Alternatively, the targets can be determined.

In some embodiments determining the targets can be based on the designdata of the wafer. In some embodiments, a synthetic image of the wafercan be created, for example rasterized, based on the design data, whiletaking into account physical properties of the wafer layers, includingcolor, thickness, opacity properties, components or the like.

The targets should have features that make them easily recognizable intheir environment. For example, they may be unique in their environment,can comprise a multiplicity of edges in one or two dimensions, possiblywith a special arrangement, or the like.

Thus, once the synthetic image is available, certain areas can beindicated as being proper targets, by applying image processingtechniques including but not limited to detection of edges, corners,blobs, points of interest, regions of interest, ridges, or the like. Thedetection may use any one or more techniques such as but not limited tohistogram of gradients, binary descriptors, deep learning techniques,entropy based identification, feature detection, or the like.

Additionally or alternatively, a smaller part of the design data can bereceived for one or more of the potential target locations; and theexact target location of each such target can be determined by applyingtechniques such as polygon processing techniques to the design data.Polygon processing may include segmenting the polygons into lines andcorners, thus dividing the potential target area to a grid of smallerregions. The uniqueness and matching scores may be calculated for eachsmaller region. The uniqueness score may be based on the similarity of apolygon to its adjacent polygons. The matching score may be based on thenumber of corners and line directions of a polygon. The smaller regionsin the potential location may then be sorted by a combination such as alinear combination of uniqueness and matching scores: score=a*uniquenessscore+b*matching score.

In some embodiments, the targets can be validated once a wafer ismanufactured. For example, the targets as determined using the syntheticimage can be compared against how the relevant area really appears, forexample by comparing to an actual image of the wafer. If a possibletarget does not comply with the criteria, for example if the edgesappear obscured for enabling proper registration, it can be deleted fromthe target collection.

Since it is not known a-priori where the review locations to be reviewedwill be located, and thus which alignment targets can be used, it willbe appreciated that having targets at high density and at substantiallyuniform distribution over the wafer, for example substantially along thelines of a two dimensional grid, can be useful for enabling properselection of the alignment targets.

Alignment target selection component 112 can be configured to performstep 212, in which a plurality of review locations to be reviewed can beobtained and accommodated in memory. The review locations can compriselocations from a larger collection of review locations reported aspossible defects by an inspection process. The review locations canfurther comprise regions of interest other than those reported by theinspection process.

Alignment target selection component 112 can be configured to performstep 216 in which a subset of the targets obtained on step 208 can beselected as alignment targets, in accordance with a received field ofview parameter and with the review locations to be reviewed. Thealignment targets can be selected such that each review location is atmost at a predetermined distance from one of the alignment targetscomprised in the subset.

It will be appreciated that the number of alignment targets selected maybe determined in accordance with considerations associated with time,cost or navigation accuracy, as detailed above.

Alignment target selection component 112 can be configured to performstep 220, in which an alignment target that meets these conditions isdetermined for each review location. In some embodiments, the selectedreview locations can be clustered, for example using a mean shiftclustering algorithm or K-means clustering algorithm with a kernel, orothers. Thus each cluster is associated with one of the receivedtargets, and all review locations in a cluster are at most at apredetermined distance from the target. Having a sufficient number andhigh density of targets enables clustering with such conditions. Thecollection of all the targets associated with the clusters makes thealignment targets.

The distance may also be regarded as a radius of a circle around thealignment target in which all review locations of the cluster arepositioned. Thus, the distance can be selected such that the maximalerror accumulated when the wafer is moved relative to the review toolfrom the alignment target to any of the review locations still maintainsthe review location within the field of view, and no further correctionis required. For example, the distance can be determined in accordancewith a formula or a look up table that associates distances on the waferwith accumulated navigation error. In one example, a distance of 1 mmbetween objects may imply an error of 100 nanometers, a distance of 2 mmmay imply an error of 250 nanometers, or the like. Thus, the distancebetween each review location in a cluster and the alignment targetassociated with the cluster should not exceed a value whose associatederror exceeds an error acceptable to a user.

The alignment targets can be stored, for example by storing thelocation, and optionally an image or another visual description of eachalignment target.

Additionally or alternatively, a coverage area may be associated witheach selected alignment target, wherein the size of each coverage areamay be responsive to the desired accuracy of the navigation process andto the expected navigation errors. It will be appreciated that steps 216and 220 can be performed together as one process, separately, with step220 being performed as part of step 216, or the like.

Once the alignment targets are selected, a global or coarse alignmentprocedure using up to a predetermined number, for example up to 12targets on the entire wafer, may ensure that the alignment target itselfcan be reached and found within a reasonable field of view. Then eachreview location can be captured and reviewed at step 154.

Examination component 100 can perform review location reviewing step 154which can comprise target alignment steps 222, that can be performedonce per cluster, such that when capturing two or more review locationsassociated with one cluster, steps 222 need not be repeated.

When performing target alignment steps 222, examination component 100can perform or initiate alignment step 224 in which the wafer is alignedwith the review capture device, such that the alignment targetassociated with the review location which is thus within the distancefrom the review location, can be captured by the review capture device,such as the SEM.

Examination component 100 can perform or initiate alignment targetcapturing step 228, in which the alignment target is captured. Since thefield of view of the capture device is consistent with the navigationaccuracy, the alignment target is known to be within the captured image.

Examination component 100 can be configured to perform or initiate step232, in which the alignment target can be searched for in the capturedimage. Searching can comprise locating the image or visualcharacteristics of the alignment target within the captured image,optionally using image analysis techniques, for example as described inUS Patent Application No. 2016-0035076 which is incorporated herein, orby any other known technique. The actual location of the alignmenttarget can then be determined from its location within the capturedimage.

Examination component 100 can be configured to perform or initiate step236, in which a transformation between the actual location of thealignment target and the location of the alignment target as determinedcan be performed. For example, the transformation can be expressed as a3*3 transformation matrix (when the alignment target is twodimensional). Alternatively, the transformation can be expressed as atwo dimensional vector. The transformation can represent the deviationof the alignment target from its intended location to the actuallocation, due to the navigation error or any other types of errors.

Once the transformation is available, then one or more of the reviewlocations comprised in the cluster of review locations associated withthe specific alignment can be captured.

Examination component 100 can be configured to perform or initiate step240, in which the transformation determined at step 236 can be appliedto a review location, to obtain a transformed review location. Due tothe relatively small distance between the review location and thecorresponding alignment target, the transformation can be relevant andcorrect, such that the required review location is indeed at thetransformed location.

Examination component 100 can be configured to perform or initiate step244, in which the wafer can be aligned with the capture deviceassociated with the review tool, such that the transformed reviewlocation can be captured by the capture device associated with thereview tool, such as the SEM.

Examination component 100 can be configured to perform or initiate step248, in which the transformed review location can be captured, and theimage can be reviewed.

Referring now to FIGS. 3, 4A, 4B and 4C showing exemplary illustrationsof alignment target subset selection.

FIG. 3 shows an exemplary illustration of targets and review locationsin a die.

Pane 300 of FIG. 3 shows a multiplicity of alignment targets 304 on die300.

Pane 308 comprises a multiplicity of review locations 312 on a die, suchas possible defect locations, regions of interest, or the like and pane316 shows review locations 312 and targets 304 together.

It will be appreciated that it is required to select a smaller number oftargets as alignment targets, such that substantially each reviewlocation is within a predetermined distance from one of the alignmenttargets. This requirement may be depicted graphically as each reviewlocation is within a circle of at most a predetermined radius, and whosecenter is located on one of the alignment targets. The radius of thecircle represents the clustering distance.

FIGS. 4A, 4B and 4C show three clustering options for review locations408 and alignment targets 400. In each option, a number of reviewlocations are in at most a predetermined distance from an alignmenttarget 400. Further possible targets 404 are not selected as alignmenttargets and are not used during review.

During review, an alignment target 400 can be navigated to, captured,and detected within the image, and a transformation can be determinedbetween the designated location of alignment target 400 and the actualone. Review locations 408 within a circle whose center is the alignmenttarget, can then be navigated to and captured, one by one. Once allreview locations 408 have been captured, the next alignment target 400and associated review locations 408 can be handled in the same manner.

FIG. 4A, in which fewer alignment targets are used, provides for feweralignment operations and therefore faster review and better throughput.However, since the radius of bounding circle 412 is larger than theradius of the bounding circles shown in FIGS. 4B and 4C, some reviewlocations and in particular the ones farther from the associatedalignment target 400 may deviate from the transformed location, andtheir capturing may thus be inaccurate. If review locations are notcaptured, a larger field of view may be used for the examination, whichimplies a larger number of pixels and thus time. Alternatively, morealignment operations may be required, thus also increasing theexamination time.

Reference is now made to FIGS. 5A, 5B, 5C and 5D showing exemplaryschematic illustrations of methods for using alignment targets whendetecting defects by comparing corresponding locations on adjacent diesin a wafer, in accordance with some embodiments of the disclosure.

It will be appreciated that although the squares formed by the grids inFIGS. 5A, 5B, 5C and 5D are sometimes referred to as dies of a wafer,wafers and dies constitute a non-limiting example and the figures anddescription may represent any other areas of an examined object.

When reviewing a review location suspected of being a defect, it can berequired to capture the review location, as well as a reference locationin a nearby area. For example, in addition to capturing the reviewlocation, which can be situated within a first die, a reference locationin a second die, which can be a neighbor of the first die, can also becaptured. The captured areas of the review location and the referencelocation can be compared, and if differences are spotted then it can beassumed that the review location indeed represents a defect or anuisance, but is not a false alarm.

FIG. 5A represents a global or coarse alignment case and shows asituation in which a small number, such as five, alignment targets 500are spread over a wafer. In this case all alignment targets arecaptured, and compared against the image or features found at theirexpected locations on the wafer, in order to produce a two-dimensionaloffset vector which may be global for the whole wafer. Each reviewlocation 508 can then be captured, as well as a corresponding referencelocation 504 in a neighboring or another close die. Due to the smallnumber of alignment targets, the deviation of each review location andeach reference location from the intended coordinates may be large, thusleading to inaccuracies and possible misses in capturing the reportedlocations.

In the situation depicted in FIG. 5B, local alignment is applied, inwhich an alignment target 524 is associated with each review location532, and a second alignment target 520 is associated with each referencelocation 528. Thus, the capturing of every review location 532 and everyreference location 528 requires a separate alignment, which increasesaccuracy, but the review process takes time which is longer than in thesituation of FIG. 5A.

FIGS. 5C and 5D represent situations in which the alignment targets areselected dynamically based on the review locations which it is requiredto review.

FIG. 5C depicts a situation in which review locations 548 are clustered,wherein each cluster is associated with a target 540. In addition, allreference locations 544 are located on one area, such as one die, andare associated with an alignment target 546. Thus, the number ofalignments has dropped relatively to the situation of FIG. 5B, withoutreducing accuracy. One additional alignment is required for capturingreference locations 544.

Referring now to FIG. 5C together with FIG. 6, showing a flowchart ofsteps in a method for using local alignment targets when reviewingreview locations, in accordance with some embodiments of the disclosure.In such embodiments, multiple reference locations may be captured on onedye, referred to as “reference dye”, with a single alignment target. Thereview locations may be captured each at its intended dye. Then, eachreview location may be compared to the corresponding location ascaptured on the reference dye.

FIG. 6 depicts steps which can be performed by a system or componentsuch as examination component 100 of FIG. 1A, after an alignment targetand a review location as transformed have been captured, as described inassociation with FIG. 2 above. Alternatively, the steps can be performedprior to capturing the alignment target and transformed review location.Since FIG. 6 involves an additional target and an additional reviewlocation, the target, the review location and the transformed reviewlocation referred to in FIG. 2 will be referred to as “the firsttarget”, “the first review location” and “the first transformed reviewlocation”.

Thus, at step 600, reference locations can be determined for two or morereview locations on one reference dye. For example, a first referencetransformed review location 549 for first review location 548, secondreference review location 544 for second review location 547, may bedetermined on reference dye 542. A reference alignment target, such asreference alignment target 546 can be determined as a common alignmenttarget for multiple reference review locations, on the same referencedye 542.

Thus, one or more reference review locations, as well as the referencealignment target may be on one reference die, which is different fromthe dies of the review locations.

At step 604, the wafer can be moved, and reference alignment target 546can be captured.

At step 608, the actual location of the reference alignment target canbe determined, by locating reference alignment target 546 in thecaptured image and determining its coordinates.

At step 612 a reference transformation can be determined, between theintended location of the reference alignment target and its actuallocation.

At step 616 a transformed first reference location can be determined, byapplying the reference transformation to the first reference reviewlocation 549.

At step 620 the wafer can be moved and first transformed referencelocation can be captured.

At step 624 a second transformed reference location can be determined,by applying the reference transformation to a second reference reviewlocation 544 corresponding to a second review location 547.

For clarity, the first transformed reference location and the second atransformed reference location are not depicted in FIG. 5C separatelyfrom the first and second review locations.

At step 628 the wafer can be moved and a second transformed referencelocation can be captured.

At step 632, subject to differences found when comparing the image areasat the first transformed review location and at the first transformedreference location, a defect in the wafer can be reported. It will beappreciated that the same comparison can be done also for transformedsecond review location 547 and a second transformed reference location544.

Thus, one additional alignment is performed, using the referencealignment target, for capturing a multiplicity of reference reviewlocations.

However, in some cases taking reference images from dies which are farapart from each other can add noise or deformations to the referenceimage and make the comparison difficult and less effective. Such noisecan be caused by the process variations, or by deformations caused by along review process.

Hence comparison with closer dies may be preferred, as detailed inassociation with FIGS. 5D and 7 detailed below, that show a flowchart ofsteps in a method for using alignment targets when reviewing reviewlocations, in accordance with some embodiments of the disclosure.

FIG. 5D depicts a situation in which for two or more review locationshaving one associated alignment target on the same dye or on a closedye, reference locations are determined on the same dye as the alignmenttarget.

Thus, for review locations 588 and 589, and associated alignment target580, reference locations 584 and 585 are added on the same die asalignment target 580. Selecting the reference locations on the same dieas the alignment target adds no alignments beyond those required for thereview locations. On the other hand, the reference locations are closeto the review locations, thus avoiding further errors.

It will be appreciated that in some embodiments, a primary and asecondary target may be associated with each region of the wafer or witheach review location, such that if, for some reason, the primary targetis inappropriate, the secondary one may be used.

FIG. 7 depicts steps which can be performed by a system or componentsuch as examination component 100, after an alignment target and atransformed first review location have been captured, as described inassociation with FIG. 2. Since FIG. 7 involves additional reviewlocations, the review location and the transformed review locationreferred to in FIG. 2 will be denoted “the first review location” and“the first transformed review location”.

At step 700, first and second reference review locations 585, 584 can bedetermined for first and second review locations 588, 589 associatedwith a common alignment target 580. Although the first and second reviewlocations 588, 589 may be in different dies, the reference locations584, 585 and alignment target 580 are on the same die which is close toreview locations 588, 589, thus avoiding errors caused by processvariations and temperature deformations.

At step 704, a first transformed reference location can be determined,for example by applying the transformation determined at step 236 ofFIG. 2 to the first reference review location 585.

At step 708, the wafer can be moved and the first transformed referencelocation can be captured by a capture device associated with the reviewtool.

At step 712, a second transformed reference location can be determined,for example by applying the transformation determined at step 236 ofFIG. 2 to the second reference review location 584.

For clarity, the first transformed reference location and the secondtransformed reference location are not depicted separately from thefirst and second review locations.

At step 716, the wafer can be moved and the second transformed referencelocation can be captured by a capture device associated with the reviewtool.

At step 720, subject to differences found when comparing the image areasat the first transformed review location 588 and at the firsttransformed reference location 584, a defect in the wafer can bereported. It will be appreciated that the same comparison can be donealso for the second transformed review location 585 and at the secondtransformed reference location 589.

Thus, no additional alignment is performed for capturing a multiplicityof reference review locations, thus improving throughput of the system.

Thus, the situations in FIGS. 5C and 5D utilize the alignment targetsfor reducing the number of required alignments and thus shortening thereview process, while maintaining accuracy by using local alignmenttargets, and in the embodiment shown in FIG. 5D also taking advantage ofcomparisons between nearby locations.

It will be appreciated that the methods disclosed above can be used as asingle alignment method, but also in conjunction with any otheralignment method, such as global alignment, dye column registration, orthe like.

Reference is now to made FIG. 8, illustrating a functional diagram of asystem for examining a wafer, in accordance with some embodiments of thedisclosure.

The illustrated system can comprise a computing platform 800,implementing examination component 100 and configured to execute themethods of FIG. 2, FIG. 6, and FIG. 7, and being operatively coupled towafer movement control and capture devices. Computing platform 800 canfurther implement alignment target selection component 112. It will beappreciated however, that alignment target selection component 112 canbe performed by another computing platform operatively coupled tocomputing platform 800.

Computing platform 800 can comprise a storage device 804. Storage device804 can be a hard disk drive, a Flash disk, a Random Access Memory(RAM), a memory chip, or the like. In some exemplary embodiments,storage device 804 can retain program code operative to cause processor812 to perform acts associated with any of the subcomponents ofcomputing platform 800.

In some exemplary embodiments of the disclosed subject matter, computingplatform 800 can comprise an Input/Output (I/O) device 808 such as adisplay, a pointing device, a keyboard, a touch screen, or the like. I/Odevice 808 can be utilized to provide output to and receive input from auser.

Computing platform 800 can comprise one or more processor(s) 812.Processor 812 can be a Central Processing Unit (CPU), a microprocessor,an electronic circuit, an Integrated Circuit (IC) or the like. Processor812 can be utilized to perform computations required by computingplatform 800 or any of its subcomponents, such as steps of the method ofFIG. 2, FIG. 6 and FIG. 7.

It will be appreciated that processor 812 can be configured to executeseveral functional modules in accordance with computer-readableinstructions implemented on a non-transitory computer-readable storagemedium. Such functional modules are referred to hereinafter as comprisedin the processor.

The components detailed below can be implemented as one or more sets ofinterrelated computer instructions, executed for example by processor804 or by another processor. The components can be arranged as one ormore executable files, dynamic libraries, static libraries, methods,functions, services, or the like, programmed in any programming languageand under any computing environment.

Processor 812 can comprise alignment target selection component 112 forreceiving a collection of targets, a collection of review locations tobe reviewed, and an accuracy parameter and determines alignment targets.

Alignment target selection component 112 can be configured to compriseclustering module 820 which can comprise one or more clustering engines,such as K-means clustering with a kernel, mean shift clustering, or thelike.

Processor 812 can be configured to comprise image analysis module 824for analyzing images. For example, image analysis module 824 cancomprise alignment target searching module 828 for locating an alignmenttarget upon its image or one or more graphic features within an image.Image analysis module 824 can comprise comparison module 832 forcomparing locations within two images and determining whether they aresubstantially the same. If the images are substantially the same, thenit can be assumed that there is no defect in any of them. If the imagesare different, then at least one of them is defected, most likely theone reported as possible defect by the inspection process.

Processor 812 can be configured to comprise navigation and capturemodule 834 for controlling the moving of a wafer to a particularlocation relative to the capture device such as the SEM and initiatingthe capturing. It will be appreciated that moving and capturing thewafer can be controlled by another computing platform which can receivecommands, send commands, or be otherwise operatively connected tocomputing platform 800.

Processor 812 can be configured to comprise transformation calculationcomponent 836 for determining transformation between two points, twolines, or two two-dimensional shapes, in order to determine thedeviation caused by navigation errors, spatio temporal errors, or thelike.

Processor 812 can be configured to comprise transformation applicationcomponent 840 for applying a transformation to a point, a line or ashape, such that the point, line, or shape undergoes the sametransformation as an alignment target associated with the location.

Processor 812 can be configured to comprise reference determinationcomponent 842 for determining reference locations to review locationswhen required, for example when the review locations have to be comparedagainst corresponding reference locations in another die, or the like.Reference determination component 842 can also determine referencealignment targets, located in relative corresponding locations toalignment targets, but in another area such as another die of the wafer.

Processor 812 can be configured to comprise one or more communicatingcomponents 844 for communication with other devices, such as inspectionor review tools, capture devices, databases, or the like.

Processor 812 can be configured to comprise user interface 852 forreceiving input from a user or providing output to a user, such asaccuracy level, regions of interest, or the like. User interface 852 canexchange information with a user by utilizing I/O device 808. It isnoted that the teachings of the presently disclosed subject matter arenot bound by the computing platform described with reference to FIG. 8.Equivalent and/or modified functionality can be consolidated or dividedin another manner and can be implemented in any appropriate combinationof software with firmware and/or hardware and executed on one or moresuitable devices.

The system can be a standalone entity, or integrated, fully or partly,with other entities, which can be directly connected thereto or via anetwork.

It is also noted that whilst the method of FIG. 2, FIG. 6 and FIG. 7 canbe performed by the system of FIG. 8, this is by no means binding, andthe operations can be performed by elements other than those describedherein, in different combinations, or the like. It is also noted thatthe teachings of the presently disclosed subject matter are not bound bythe flow charts illustrated in FIG. 2, FIG. 7 and FIG. 8, and theillustrated operations can occur out of the illustrated order.

It is to be understood that the disclosure is not limited in itsapplication to the details set forth in the description contained hereinor illustrated in the drawings. The disclosure is capable of otherembodiments and of being practiced and carried out in various ways.Hence, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting. As such, those skilled in the art will appreciatethat the conception upon which this disclosure is based may readily beutilized as a basis for designing other structures, methods, and systemsfor carrying out the several purposes of the presently disclosed subjectmatter.

It will also be understood that the system according to the presentdisclosure may be, at least partly, implemented on a suitably programmedcomputer. Likewise, the disclosure contemplates a computer program beingreadable by a computer for executing the method of the disclosure. Thedisclosure further contemplates a non-transitory computer-readablememory tangibly embodying a program of instructions executable by thecomputer for executing the method of the disclosure.

Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of thedisclosure as hereinbefore described without departing from its scope,defined in and by the appended claims.

What is claimed is:
 1. A method comprising: receiving data indicative ofa plurality of alignment targets, each alignment target of the pluralityof alignment targets being associated with a corresponding targetlocation on a physical object; identifying a plurality of locations onthe physical object to be inspected; selecting, by a processor, analignment target from the plurality of alignment targets, wherein eachof the plurality of locations is within a determined distance from theselected alignment target; and providing an indication to align, usingthe selected alignment target, the physical object relative to anexamination tool for inspecting the plurality of locations within thedetermined distance from the selected alignment target.
 2. The method ofclaim 1, wherein each of the plurality of locations corresponds to apotential defect, and wherein the physical object corresponds to asemiconductor wafer.
 3. The method of claim 1, wherein the determineddistance is based on a field of view associated with the physicalobject.
 4. The method of claim 1, further comprising: receiving an imageassociated with the physical object; identifying the selected alignmenttarget from the image; and determining coordinates of the selectedalignment target, wherein the indication is based on the determinedcoordinates.
 5. The method of claim 4, further comprising: applying areference transformation to the selected alignment target based on thedetermined coordinates to determine another location associated with theselected alignment target.
 6. The method of claim 5, further comprising:providing a second indication to move the examination tool to capture aparticular location of the plurality of locations based on the anotherlocation.
 7. The method of claim 5, wherein the reference transformationis a two dimensional transformation.
 8. A non-transitory computerreadable medium comprising instructions, which when executed by aprocessor, cause the processor to perform operations comprising:receiving data indicative of a plurality of alignment targets, eachalignment target of the plurality of alignment targets being associatedwith a corresponding target location on a physical object; identifying aplurality of locations on the physical object to be inspected; selectingan alignment target from the plurality of alignment targets, whereineach of the plurality of locations is within a determined distance fromthe selected alignment target; and providing an indication to align,using the selected alignment target, the physical object relative to anexamination tool for inspecting the plurality of locations within thedetermined distance from the selected alignment target.
 9. Thenon-transitory computer readable medium of claim 8, wherein each of theplurality of locations corresponds to a potential defect, and whereinthe physical object corresponds to a semiconductor wafer.
 10. Thenon-transitory computer readable medium of claim 8, wherein thedetermined distance is based on a field of view associated with thephysical object.
 11. The non-transitory computer readable medium ofclaim 8, the operations further comprising: receiving an imageassociated with the physical object; identifying the selected alignmenttarget from the image; and determining coordinates of the selectedalignment target, wherein the indication is based on the determinedcoordinates.
 12. The non-transitory computer readable medium of claim11, the operations further comprising: applying a referencetransformation to the selected alignment target based on the determinedcoordinates to determine another location associated with the selectedalignment target.
 13. The non-transitory computer readable medium ofclaim 12, the operations further comprising: providing a secondindication to move the examination tool to capture a particular locationof the plurality of locations based on the another location.
 14. Thenon-transitory computer readable medium of claim 12, wherein thereference transformation is a two dimensional transformation.
 15. Asystem comprising: a memory; and a processor, operatively coupled withthe memory, to: receive data indicative of a plurality of alignmenttargets, each alignment target of the plurality of alignment targetsbeing associated with a corresponding target location on a physicalobject; identify a plurality of locations on the physical object to beinspected; select an alignment target from the plurality of alignmenttargets, wherein each of the plurality of locations is within adetermined distance from the selected alignment target; and provide anindication to align, using the selected alignment target, the physicalobject relative to an examination tool for inspecting the plurality oflocations within the determined distance from the selected alignmenttarget.
 16. The system of claim 15, wherein each of the plurality oflocations corresponds to a potential defect, and wherein the physicalobject corresponds to a semiconductor wafer.
 17. The system of claim 15,wherein the determined distance is based on a field of view associatedwith the physical object.
 18. The system of claim 15, wherein theprocessor is further to: receive an image associated with the physicalobject; identify the selected alignment target from the image; anddetermine coordinates of the selected alignment target, wherein theindication is based on the determined coordinates.
 19. The system ofclaim 18, wherein the processor is further to: apply a referencetransformation to the selected alignment target based on the determinedcoordinates to determine another location associated with the selectedalignment target.
 20. The system of claim 19, wherein the processor isfurther to: provide a second indication to move the examination tool tocapture a particular location of the plurality of locations based on theanother location.